How to Replicate an Artifact in Concrete




About: I like to make things more simple with easily available resources. My favorite quote: A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write...

My last Instructable was about making "A Small Bedside Coffee Table in Concrete" using easily available household items,  which you can view at this link:

This Instructable will provide you step-by-step guide on how to replicate an artifact in concrete using a mold made of silicone rubber.

I came across this piece of art of 'a mother bird feeding its chicks on a tree branch' and wanted to make a copy of that. So I borrowed the piece, made a mold out of silicone rubber and using that mold cast it in concrete.

Look at the original and the replications in these pictures.. Though there are some imperfections in the replication, they can be corrected using a paste made of white cement and cement pigment. Also. for drawing the eyes and all, I will get some friends' help as I am not good at that.

Step 1: How to Make the Silicone Mold...

To replicate this art piece, one of the most suitable mold making material which can bring out the intricate details is Silicone Rubber. I have used Silicone mold making material VITSPEC VSGI-1220. This material comes in two parts, the Base and the Activator. With the 5 kilogram pack of the Base, a 250 grams Activator is included. That means, for every 1000 grams of base, you need to add 50 grams of Activator. After activation, it will take a minimum of 24 hours to fully cure.

  • Select a suitable container to hold the piece to be replicated and the silicone mix.
  • Roughly calculate the amount of silicone mix needed for the job. I have calculated that I need about 1500 grams of Silicone mix.
  • Take a container and weigh about 1500 grams of base.
  • Add 75 grams activator to the base and mix well. it is recommended to pour the mix back in another container and mix again uniformly.
  • Spray the art piece and the container with silicone spray, which will act as mold release.
  • Pour the silicone mix over the container from a height of about 12 inches, starting from the exposed lower end and follow it up so that the mix naturally flows up and covers all the curves, nooks and corners without trapping any air bubbles.
  • After completely filling up the container, leave it undisturbed for about 24 hours.
  • After 24 hours, lightly touch the top surface of the silicone mix. If it sticks to your fingers, give it more time to cure. As the quantity of mix is more, it took about 48 hours in my case.
  • When the silicone mix is not sticky to touch, you can take out the mold out of the container and release the art piece.

Now your Silicone mold is ready. You can replicate as many pieces of the original as you like, using this silicone mold. You can use it for concrete, wax cast and casting with Plaster of Paris.

Let us see how we can cast the art piece in concrete.

Step 2: Making a Dry Mix of Concrete

Making the dry mix for the concrete work:

  • Sieve the required quantity of sand with a fine sieve to remove the coarser particles.
  • Measure one part of white cement and two parts of sieved sand.
  • Add a table spoon of cement based color pigment to the dry mix. I have used black color pigment here.
  • Mix well using a ladle to form a uniform dry mix.

Now the dry mix required for the concrete is ready.

Step 3: Concreting the Mold

Concreting the mold:

  • Add little amount of water at a time to the dry mix and mix thoroughly.
  • The concrete should contain only enough water for proper filling of the mold and not more than required.
  • Keep the mold on a piece of thermocol or any other suitable material.
  • Transfer the mixed concrete in layers and compact with the ladle, so that all the nooks and corners are properly filled.
  • Shake the concrete holding the bottom piece. This will help in releasing any air bubbles trapped inside.
  • After some time, say about 10 to 15 minutes, you will find a layer of water forming on top.
  • Using old news paper, sponge out the excess water on top.
  • Keep the concrete undisturbed for another 24 hours

Step 4: Curing and Removing the Concrete Cast From the Silicone Mold

Curing and Removing the Concrete Cast from the Silicone Mold:

  • After 24 hours of casting, place the mold upside down in cold water. This is to prevent any deformation to the top  portion of the cast.
  • The mold with the concrete are to be cured for three days in cold water.
  • After three days, remove the mold from water and carefully remove the cast.
  • You can place the demolded piece in water for another one week for more curing.

Now your replicate in concrete is ready...

Step 5: Bottom Line

The silicone mold we made can be used repeatedly for replicating the original piece. You can use wax, plaster of Paris, concrete and any other suitable material for casting. You can also color your work with cement based colors and make it more attractive.

Please enjoy the pictures of the same piece molded in wax and Plaster of Paris here...

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    14 Discussions


    4 years ago on Introduction

    Please advise where we could buy the Silicone mold making material VITSPEC VSGI-1220 in Chennai or advise me the contact details anywhere in India

    1 reply

    Reply 4 years ago on Introduction

    I am not aware of dealers in Chennai. Please contact the below address for silicon related products. Their product may not be VITSPEC VSGI-1220, but they have similar product. Please also mention what you are going to use the product for.

    Yogesh Walzade.
    Link Composites Pvt ltd
    Plot No: 3B+3, Unit No: 6, D-1 Block, MIDC,
    Opp. Ador Welding Ltd, Chinchwad, Pune 411019
    Tel No: 9657716031, 30724590


    5 years ago on Introduction

    whew. I am going to have to work hard to be nice. You do not use silicone spray as a release agent when pouring silicone: it acts as a thinner and brings silicone rubber deep into the texture of the original. You use thinned vaseline. I am unfamiliar with your brand of silicone but with more ordinary casting silicones, like GI-1000, you can count on it to be cured after 16 hours, and using more makes it surer it will be cured. Only old material might cure slower.

    7 replies

    Reply 5 years ago on Introduction

    I have gone through your website and your works are amazing. I am not a professional like you. I sought the advice of the vendor when I purchased the silicone spray and he confirmed that it can be used as mold release. You can also see the description of the material on its cover. Secondly, the instruction on the containers of silicone mold making material I used stats that it needs 24 hours curing.


    Reply 4 years ago on Introduction

    Please advise where we could buy the Silicone mold making material VITSPEC VSGI-1220 in Chennai or advise me the contact details anywhere in India


    Reply 5 years ago on Introduction

    The last thing I want to do is make you feel bad.. The only thing I want to do is replace bad info with good info, as quick as possible. In the photo you included, maybe the pertinent info is above the top edge.
    When you are wanting to cast concrete, plaster, or wax, may as well go with cheaper, tougher urethane rubber. Silicone is needed when casting urethane resins (urethanes "want to" marry.)
    Sometimes they say 16 hour cure meaning, Do the pour at the end of the day, open the mold the next morning.
    You should have got better detail, such as in the bird mouths.


    Reply 5 years ago on Introduction

    As an expert on these things, will you post an instructable explaining all these things....? I could not find any in your page other than comments...


    Reply 5 years ago on Introduction

    I started an Instructable of a very simple one-board bench and saw that clear photos and explanations of decision-making are harder than I thought! But at the top of my Archicast main page, find a step-by-step for the making of Goliath. Also using an obsolete Mac which frustrates me constantly.
    I wrote a couple of long essays on materials such as concrete on a sculpture newsgroup, they're out there.


    Reply 5 years ago on Introduction

    There is no link in "See the creation of Goliath" in your web-site. May be some error. I am very much interested in going through that.. It is there on top of your site but leads to nowhere